This idiom or expression has to do with:

Doing things in the opposite order.
Reversing the proven or accepted order of doing things.

This idiom or expression means:

You must decide now.
You can’t wait any longer.
It’s time to make a decision.

This idiom or expression means:

Arrogant.
Inflexible.
Condescending.
Looking down on others.

A. Why don’t you like my friend?
B. He always gets on his high horse, no matter what subject we're talking about.
A. Well, that’s easy. Just tell him to get off his high horse!!!

Also, related:
Off one’s high horse.

Know your capabilities and limits.

This idiom or expression like phrase means:

Underdog.
A promising, but previously unknown, political candidate.
Someone you don’t expect to win, but who ends up winning.

This idiom or expression has to do with:

Talking about something that has already been decided.
Wasting one’s time talking about something that won’t change.

A. Can we talk about my trip now?
B. Come on, stop beating a dead horse! We’ve already decided you’re not going.

This idiom or expression like sentence means:

I'm very hungry.